Those arrested "were the main players in the recent fluctuations in the foreign currency market," the Tehran Judiciary said in a statement.

The move came a day after riot police worked to disperse protests in the capital's main bazaar and nearby streets. Demonstrators chanted slogans opposing firebrand President Mahmoud Ahmadinejad and decrying the skyrocketing cost of basic goods.

Some "agitators" and two European tourists who were gathering information about the protests were arrested Wednesday, the semi-official Mehr news agency reported.

The rial's plummet to historic lows is the result of international sanctions, imposed largely by the United States and the European Union in an effort to pressure Iran to sit down for talks on its nuclear program.

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"Our goal has been and remains to persuade the Iranian regime to negotiate seriously in good faith with the international community over its nuclear program, to fulfill its obligations to the International Atomic Energy Agency and to the United Nations and to do so expeditiously," U.S. Secretary of State Hillary Clinton said Wednesday.

Ahmadinejad and the country's supreme leader, Ayatollah Ali Khamenei, have assailed the sanctions, insisting "the enemy" will fail in its efforts and is hurting the Iranian people rather than the government.

But the protesters Wednesday made clear their anger with the president. The bazaar closed, but was open and apparently back to normal on Thursday, with only a few shops still closed.

Ahmadinejad, in a speech this week, also said blamed "22 ringleaders" who the country's intelligence services have determined are causing tension and manipulating currency.

While he gave no details, people who trade currency on the black market have been increasingly concerned about a crackdown by Iranian forces.

The government did not identify the 16 arrested Thursday. In a written statement, the judiciary said they "had used an atmosphere of psychological war created by the enemy" and colluded with "certain domestic and foreign groups" to exacerbate conditions."

They traded extensively in "smuggled" currencies "outside of the banking network" in order to increase the value of foreign currencies and disturb the public, the judiciary claimed, adding that they "amassed illegal fortunes."

One of the accused had $300 million going through a bank account, the statement said.

Iran warned that others "are being accused as well and will be dealt with soon."